Series transformer connection



Dec. 8, 1931. Q us 1,835,199

7 SERIES TRANSFORMER CONNECTION Filed July 2, 1926 Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE I ARTHUR O. AUSTIN, 0F BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY.

SERIES TRANSFORMER CONNECTION Application filed July 2,

This invention relates to high tension transformer systems and has for its object the provision of an improved arrangement of transformers which will produce an addi- 5 tion of the secondary voltages of the transformers while maintaining unimpaired regulation and providing for increased power output and which will permit economical construction and operation.

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification and it is more particularly pointed out in the appended 15 claims.

In the drawings- Fig. 1 is a diagrammatic view of transformer connections according to one embodyment of the present invention.

Figs. 2 and 3 are views similar to Fig. 1 showing different embodiments of the invention.

It is a difiicult matter to construct and arrange a single transformer for exceedingly high voltages as the maximum Voltage or tension to ground requires an abnormal amount of clearance or insulation compared to that required for transformers of lower voltage. The chain or concatenated connection of transformers in which each transformer is energized from the preceding transformer in the chain permits the tieing together of transformers in series so that the voltages are additive- This. arrangement permits of obtaining a very high voltage with individual transformers built for moderate voltages.

In the concatenated or chain system of connection however as illustrated, for in stance, inUnited States Patent 1,523,367 the KVA (kilovolt-ampere) output of the chain is limited to the KVA output of the smallest or most highly loaded transformer in the series or chain. In other words, if there are four transformers having 500 KVA output each, the maximum KVA output would be limited to 500 KVA. If one of the transformers in the serieshad only 300 K VA output* when the/transformer was developing itsgfnaximum rated current or voltage, the

1926. Serial No. 120,088.

KVA output of the series would be limited to this figure.

In my improved method of connecting up transformers it is possible greatly to increase the KVA output of the series thereby permitting the use of smaller transformers for a given total KVA output. With the improved method, it is also possible to obtain a much better regulation which is beneficial in case the transformers are desired for power purposes or for determining the voltage on the high side for test purposes.

In Fig. 1 are shown two transformers with cores 8 and 9, secondaries 10 and 11 and corresponding primaries 12 and 13. The end of the winding 10 is electrically connected to the case and core at 14. The secondary of the other transformer is electrically connected to its case and core at 15 and thepoints 14 and 15 are electrically connected together. The primaries 12 and 13 of the transformers are electrically connected at one end to the core and case which willmaintain a definite difference in voltage between the other end of the winding and core and case. The primary 1 windings 12 and 13 are shown connected in multiple, but it is evident that these windings may be connected in any of the usual ways. The winding of the secondary 10 is brought out through a high voltage bushing at 16 and connected to ground. The other end of the secondary winding 10 which is connected to the case and core at 14 is connected at 15 to the end of the secondary 11. The other end of the secondary 11 is brought out through a high voltage bushing at 17. Assumin that the transformers will each develop 500 V., it will be possible to develop 1,000 K. V. with this arrangement without placing any more electrical stress on the parts of the transformer than would be obtained were the transformers used singly. In order to do this it is, of course, necessary to insulate the transformers from ground so that they will both carry the voltage developed in the winding 10 of the first transformer. The generator used for exciting the transformers will also have to be insulated for this same voltage. This is a comparatively easy matter as the generator may be driven by an insulated 10! belt such as a rubber belt or through an insulated coupling. 1f the generator is provided with a motor which can be operated by air, oil, dry steam or 'otherrnon-conductor which is caused to flow through an insulating hose on tube, the =mever operating the. generato rmay'be operated directly with" the-generator.

It is evident that if the two cores were cm- *bind "nto onef-the p v Fig. 1= e0ri-esp0nds e0= single l transformer with the center point grounded. It Will be to ground and hasthe niid'dleof the high potential} w indiiig electrically connected to iih'e case can be operated at full voltageto'ground .rby the abeve 'inethod i where the caseis insi lated' a from g-round. In general, :it is cheaper 1 to {build transformerswhich I have the-. high voltage -wind ing;. grounded on the core-and case in thecenterratherj than at one e'n (h as the fvoltage between i secondary and core; andfc ase is' oi ly half what =it-i s y'vh'ereone end ef the secondary is grounded as in Fig. 1. lnw'lfllig. 2- isshoWn an arrangementof transformers M'vhere the center er l the high vol-tage'z-win'ding -in one transformer is connected to tl'leflflfs and -core-whereasl the end efuthe liiglr voltagesecondary winding 'of the ort-herztransformen oirly: isz connected @to its case and-core although the two transformers are arrangedso thatwtheir voltage willtbe aceuniulative as in the-case ofi-Fig. 1.

yI "Eigi-2 twqsgeneratorsare used as there -will-be=a-verysgeppreciable diiference in vo'lt- Qg6=' -b6l W6I1-l3hG- COIQS' and casesin the two transformers ln the arrangement shown in *1 A ameyofagenerator v18 may 'be grounded; th'usxmaking-this; gener'a tor easy to eontrolias to-vo'ltage and 5 general ope'rtion. Generator -19 operating ther'second transformenmusebe insulated as the difference :in vbltage between this "generator and; "ground iii ld be olta generated flin' thesecaryjwinding 2Q 1a usz1/ tllQVOltitgGzgGllBI rated. an the secondary winding 21. The 0W0 .gener a'torsi may -l-be kept in synch-ronismr. by alri i ati roug f synchronous motorsiwhieh RI'QflIlVUl f-rom the same power source, the synchronous 'Emot'ors 1 being'= rigidly: coupled to thegenerators ;l8 and :--19--so that: proper phase relation will-be maintained. For inost work--.it is; not even necessary that? the two 5 -generators be driven in synchroni-sm at all times. Item of thez'generatorsis? connected to awariables'peed i'r'notori'it is possible to so .re'gu-l ate lthei speed hithat :the voltage in: the

"two tran s-formersfmayhave proper; kphase -re= gee lation: E This may 'beideterm inedwery simply -nrismindiQ-tingidevices. 7 V

lIn allcases wheref'anz insulated generator is eed-at; 'of course-is necessary to insulate the exciter or. JZOWHSE st storage batteryfor exr-rarigement shown "in tr als secondary=8O e1ecti'ica1ly connectd to tlie coreand case and the ether transformer A, has the center of. the secondary 31 electrically seen with this arrangement thata' transformer which is ordinarily Wound forhalf voltage arrangement itvis pessibl'e rgrea t l 9 citation which may be readily insulated. If theyoltage of the generator 19 is set for a given value, it is usually possible to control the voltage of the series within the limits desired by controlling the Voltage of the generator18 which may be-operatedasiany gen- Gll'ti()1',fl$ the frame or winding is'i'grounded. Fig. 3 shows another arrangement of transformers Where one transformer has one end l he arrangements :described izabove h'ave'wo the advantage amongothers that-the.- maxi mum KVA output rmayi-be increasedwiththe addition ot more transformers. Practically any :number :of transformers may '=be used in series as the resulting regulation wilt-betheaes same as that for a single transformerhmider the-same conditions. wfl here' is asdecided-iadvantage with tlie'present inyentiomwhere-the accurate determination of vol tage 'ris .desired as the phase displacementwiillnotbe sogg reatiflpo and theregulation J Willi be imuch betterl than in chain or auto type connections. Jllhe scheme permitsthe 'use =ofi anyeh-igh voltage transformer a seriesiwithout the necessity 'of providingwspecial windingsw- -W -i'tlf 'the o increase the EVA outputofi a seriesiofeii inarytrans- -formers oven that =possible -where the exciting or energizing eurrentmusbbedrawn through a single aneinber int ithegig rou-p. !Wh@re' !the '10 generators can beeinsulate'd the seheme has an} application for power i-li'nexworkiasiitnwill permit the: 1 increase a anivoltage gbyvaadding transformer-s 'j to nthoseialready: in serviee. Numerous scheme twhieh are already ineuse ear syn chronizingathe generators az'm'ay -be readily used for maintaining the-jproper phas'e relation ef the seye-ral gen'erators. *"lelaim I I 1, A pair-er trarisformerseabh eomprisi ig 'a primary and a; SQfiDIiClQJIYWfidiIiQ said 'transformersfihayingtheir secoiidaryfwiiidings connectedfin series; the adjacenteiidsof said secondary windings in said s' -aries'"being grounded .on "the cores and case of "said transformers and: a generato1 1condu tivel connected with the primary windingsof said transformers? for energizing said transformer's, said genera-tor -beingansulated from Hm ground and having one terminal thereof grounded on said cores and cases.

2. A pair of transformers each comprising a primary and a secondary winding, said transformers having their secondary windings connectedin series, the adjacent ends of said secondary windings in said series being electrically connected directly to the cores and cases of said transformers while the end of one of said secondary windings at one extremity of said series is grounded and a generator conductively connected with the primary windings of said transformers for energizing said transformers, said generator having one terminal thereof directly connected electrically to the cores and cases of said transformers.

3. In combination a plurality of transformers, each comprising a primary and a secondary winding, said transformers having their secondary windings connected in series, and a generator conductively connected to the primary of one of said transformers, said generator having one terminal thereof conductively connected with the secondary windings of said transformers at a point between said windings, said generator having its frame insulated from ground.

In testimony whereof I have signed my name to this specification on this 26th day of June A. D. 1926.

ARTHUR O. AUSTIN. 

